Apparatus and method of releasing a point-to-multipoint radio bearer

ABSTRACT

A mobile terminal can release a point-to-multipoint radio bearer (RB) in an explicit manner or an implicit manner, whereby an explicit RB release mechanism allows the network to explicitly instruct the mobile terminal to release the RB, while an implicit RB release mechanism allows the mobile terminal itself to release the RB without receiving any explicit instructions from the network.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of Korean application number023071, filed Apr. 2, 2004, the disclosure of which is incorporatedherein by reference, and the benefit of U.S. provisional application No.60/541,233, filed Feb. 4, 2004, the disclosure of which is incorporatedherein by reference.

BACKGROUND

The present invention relates to releasing a point-to-multipoint radiobearer for a multicast or broadcast service in a mobile terminal, and inparticular, to determining the releasing of the point-to-multipointradio bearer by checking a status of the multicast or broadcast servicewhen a data of the multicast or broadcast service is not received for acertain period of time after the mobile terminal establishes thepoint-to-multipoint radio bearer and receives the data of the multicastor broadcast service.

A universal mobile telecommunication system (UMTS) is a third generationmobile communications system that has evolved from the European GlobalSystem for Mobile communications (GSM) that aims to provide an improvedmobile communications service based upon a GSM core network and widebandcode division multiple access (W-CDMA) wireless connection technology.

FIG. 1 illustrates an exemplary basic structure of a UMTS network. Asshown in FIG. 1, the UMTS is roughly divided into a terminal 100 (mobilestation, user equipment (UE), etc.), a UTRAN 120, and a core network(CN) 130. The UTRAN 120 includes one or more radio network sub-systems(RNS) 125. Each RNS 125 includes a radio network controller (RNC) 123,and a plurality of base stations (Node-Bs) 121 managed by the RNC 123.One or more cells exist for each Node B.

The RNC 123 handles the assigning and managing of radio resources, andoperates as an access point with respect to the core network 130. TheNode-Bs 121 receive information sent by the physical layer of theterminal 100 through an uplink, and transmit data to the terminalthrough a downlink. The Node-Bs 121, thus, operate as access points ofthe UTRAN 120 for the terminal 100. Also, the RNC 123 allocates andmanages radio resources and operates as an access point with the corenetwork 130.

Between various network structure elements, there exists an interfacethat allows data to be exchanged for communication therebetween.

FIG. 2 illustrates a radio interface protocol architecture (structure)between the terminal 100 and UTRAN 110 that is based upon 3GPP wirelessaccess network technology. Here, the radio access interface protocol hashorizontal layers including a physical layer, a data link layer and anetwork layer, and has vertical planes including a user plane fortransmitting data information and a control plane for transmittingcontrol signals. The user plane is a region to which traffic informationof a user, such as voice data or Internet-protocol (IP) packets aretransmitted. The control plane is a region to which control information,such as an interface of a network or maintenance and management of acall, is transmitted. In FIG. 2, protocol layers can be divided into afirst layer (L1), a second layer (L2) and a third layer (L3) based uponthe three lower layers of an open system interconnection (OSI) schemethat is well-known in the art of wireless (mobile) communicationsystems.

Each layer shown in FIG. 2 will now be described. The first layer (L1)uses various radio transmission techniques to provide informationtransfer service to the upper layers. The first layer (L1) is connectedvia a transport channel to a medium access control (MAC) layer locatedat a higher level, and the data between the MAC layer and the physicallayer is transferred via this transfer channel. Also, between differentphysical layers, namely, between the respective physical layers of thetransmitting side and the receiving side, data is transferred via aphysical channel.

The MAC layer handles the mapping between the logical channels and thetransport channels, and provides a re-allocation service of the MACparameter for allocation and re-allocation of radio (wireless)resources. The MAC layer is connected to an upper layer called a radiolink control (RLC) layer through a logical channel, and various logicalchannels are provided according to the type of transmitted information.

The MAC layer of the second layer (L2) provides services to a Radio LinkControl (RLC) layer, which is an upper layer, via a logical channel. TheRLC layer of the second layer (L2) can support reliable datatransmissions, and can perform a segmentation and concatenation functionon a plurality of RLC service data units (RLC SDUs) delivered from anupper layer.

A packet data convergence protocol (PDCP) layer is located at an upperlayer from the RLC layer, allowing data to be transmitted effectivelyvia a radio interface with a relatively small bandwidth through anetwork protocol.

The radio resource control (RRC) layer located at the lowest portion ofthe third layer (L3) is only defined in the control plane, and controlsthe transport channels and the physical channels in relation to theconfiguration, the re-configuration, and the releasing of the radiobearers (RBs).

The radio bearer service refers to a service that the second layer (L2)provides for data transmission between the terminal (UE) 10 and theUTRAN 100 in order to guarantee a predetermined quality of service bythe UE and the UTRAN. And in general, the radio bearer (RB)establishment refers to regulating the protocol layers and the channelcharacteristics of the channels required for providing a specificservice, as well as respectively setting substantial parameters andoperation methods.

Among the RBs, the particular RB used between the UE and the UTRAN forexchanging RRC messages or NAS messages is called a SRB (Signaling RadioBearer). When an SRB is established between a particular UE and theUTRAN, a RRC connection exists between the UE and the UTRAN. A UE havinga RRC connection is said to be in RRC connected mode, and a UE without aRRC connection is said to be in idle mode. When a UE is in RRC connectedmode, the RNC determines the cell in which the UE is located (i.e., theRNC determines the UE location in units of cells), and manages that UE.

Next, multimedia broadcast/multicast service (MBMS) will be described.MBMS refers to a downlink transmission service for providing dataservices such as, streaming services (e.g., multimedia, video on demand,webcast) or background services (e.g., e-mail, short message services(SMS), downloading), to a plurality of terminals by employing a downlinkdedicated MBMS bearer service.

MBMS can be classified into a broadcast mode and a multicast mode. TheMBMS broadcast mode refers to transmitting multimedia data to all userswithin a broadcast area, which is a region where broadcast service ispossible. In contrast, MBMS multicast mode refers to transmittingmultimedia data to only a certain specified user group within amulticast area, whereby a multicast area, which is a region wheremulticast service is possible. Thus, an MBMS service may also bereferred to as a ‘point-to-multipoint service’.

A single MBMS service can consist of one or more sessions, and MBMS dataare transmitted to the plurality of terminals via an MBMS bearer serviceduring an ongoing session.

The UTRAN uses a radio bearer (RB) to provide a MBMS bearer service to aterminal. The types of radio bearers used by the UTRAN include apoint-to-point (p-t-p) radio bearer and a point-to-multipoint (p-t-m)radio bearer. Here, the point-to-point RB is a bi-directional RB thatcomprises a logical channel (DTCH: Dedicated Traffic CHannel) and atransport channel (DCH: Dedicated CHannel), and a physical channel(either a DPCH (Dedicated Physical CHannel) or a SCCPCH (SecondaryCommon Control Physical CHannel)). A point-to-multipoint RB is auni-directional RB that comprises, as shown in FIG. 3, a logical channel(MTCH: MBMS Traffic CHannel) and a transport channel (FACH: ForwardAccess CHannel), and a physical channel (SCCPCH: Secondary CommonControl Physical CHannel). The logical channel MTCH is configured foreach MBMS service provided to a single cell, and is a channel that isused for transmitting user plane data of a particular MBMS service to aplurality of users.

The UTRAN that provides MBMS service transmits, to a plurality ofterminals, a MBMS-related control message (namely, a RRC message relatedto MBMS service data) via a MCCH (MBMS Control CHannel). Examples of anMBMS-related message include a message that informs MBMS service data, amessage that informs point-to-multipoint RB data, etc. As shown in FIG.3, the logical channel MCCH is a point-to-multipoint downlink channelthat maps to a transport channel FACH (Forward Access CHannel), whichmaps to a physical channel SCCPCH (Secondary Common Control PhysicalCHannel). For a single cell, only one MCCH exists.

A terminal wishing to receive a particular MBMS that uses apoint-to-multipoint RB, first receives via the MCCH, a RRC message thatincludes RB data, and then the point-to-multipoint RB is establishedwith the terminal using such RB data. Thereafter, the terminal continuesto receive the physical channel SCCPCH (to which the MTCH is mapped) andobtains the data of the particular MBMS service being transmitted viathe MTCH.

When one session of a particular MBMS service that uses apoint-to-multipoint RB is completed, the UTRAN transmits a message thatinstructs the release of the point-to-multipoint bearer, via the MCCH tothe terminals that are receiving the particular MBMS service. Also, theUTRAN releases the point-to-multipoint RB established at the RNC andNode B. Meanwhile, a terminal that has received the above-identifiedmessage releases the point-to-multipoint RB that had been establishedwith the terminal for the particular MBMS service.

While a particular MBMS service is in progress, one or more sessions forthat service may occur in sequence. Here, a session may be defined invarious ways. For example, a session may be each complete episode of amulti-episode drama or a session may be certain portions of a sportsprogram, such as scenes that show goals in a soccer match.

When data to be transmitted for a particular MBMS service is generatedat the MBMS data source, the core network (CN) 130 informs a sessionstart to the RNC 123. In contrast, when there is no further data at theMBMS data source to be transmitted for a particular MBMS service, thecore network (CN) 130 informs a session stop to the RNC 123. Between thesession start and the session stop, a data transfer procedure for theparticular MBMS service can be performed. Here, only those terminalsthat have joined a multicast group for the MBMS service may receive datathat is transmitted by the data transfer procedure.

In the above session start procedure, the UTRAN that received thesession start from the core network (CN) transmits an MBMS notificationto the terminals. Here, MBMS notification refers a function of the UTRANfor informing a terminal that the transmission of data for a particularMBMS service within a certain cell is impending. The UTRAN can use theMBMS notification procedure to perform a counting operation thatdetermines the number of terminals that wish to receive a particularMBMS service within a particular cell. The counting procedure is used todetermine whether the radio bearer for providing the particular MBMSservice should be set as point-to-multipoint (p-t-m) or point-to-point(p-t-p). For selecting the MBMS radio bearer, the UTRAN internallyestablishes a threshold value. After performing the counting function,the UTRAN may set a point-to-point MBMS radio bearer if the number ofterminals existing within the corresponding cell is smaller than thethreshold value, and may set a point-to-multipoint MBMS radio bearer ifthe number of terminals existing within the corresponding cell isgreater than or equal to the threshold value.

If a point-to-point radio bearer is to be set, the UTRAN allocates adedicated logical channel to each terminal (UE) and sends the data ofthe corresponding service. If a point-to-multipoint radio bearer is tobe set, the UTRAN uses a downlink common logical channel to send thedata of the corresponding service.

In the related art, the terminals that receive a particular MBMS serviceupon establishing a point-to-multipoint RB, release the establishedpoint-to-multipoint RB only after they receive a message from the systeminstructing that the point-to-multipoint RB should be released. However,in this case, those terminals that do not receive such message due topoor radio environment conditions or operation errors, cannot properlydetermine when the established point-to-multipoint RB should bereleased.

Accordingly, if the terminal is in a temporary data reception pausestate and release of the RB is prematurely performed, the terminalcannot receive any MBMS service data that was transmitted after thetemporary data reception pause. Also, if the terminal could notdetermine whether the RB should be released and thus releasing of the RBis not performed when necessary, the terminal must continue tounnecessarily maintain the point-to-multipoint RB, which thus results ina waste of terminal resources. Namely, in the related art, the terminalcannot distinguish between a temporary data reception pause and a RBrelease situation, and thus cannot properly determine when thepoint-to-multipoint RB should be released. This results in a problem forthe terminal of not being able to effectively control the operations ofmaintaining and releasing a radio bearer. Thus, the inventors of thepresent invention recognized such drawbacks of the related art andprovided a solution by allowing the terminal (UE) to release apoint-to-multipoint radio bearer in either an explicit manner or animplicit manner, to be explained in more detail hereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, nature, and advantages of the present invention willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout and wherein:

FIG. 1 depicts an exemplary basic structure of a UMTS network.

FIG. 2 depicts a radio access interface protocol architecture betweenthe terminal and UTRAN that is based upon the 3GPP wireless accessnetwork.

FIG. 3 depicts an example of channel mapping for MBMS in the terminalside.

FIG. 4 depicts an exemplary method of detecting whether a data unit(packet) is received by the terminal according to the present invention.

FIG. 5 depicts an exemplary method of releasing a point-to-multipointradio bearer according to the present invention.

FIG. 6 depicts an exemplary communications system according to thepresent invention.

DETAILED DESCRIPTION

The following description is based upon the presently preferredexemplary and non-limiting embodiments of the present invention. Moreparticularly, various inventive concepts and principles embodied insystems and methods therein are discussed and described.

The present invention was developed in order to overcome the problems ofthe conventional art. Namely, a purpose of the present invention is toprovide a mobile terminal (e.g., mobile station, user equipment (UE),etc.) that effectively controls the maintaining and releasing of a radiobearer (RB), by establishing a point-to-multipoint RB, receiving data ofa multicast or broadcast service (e.g., a MBMS service, apoint-to-multipoint service, etc.), and determining when to release thepoint-to-multipoint RB by checking the status of the multicast orbroadcast service if data of the multicast or broadcast service is notreceived for a certain period of time.

A method for releasing the RB by a mobile terminal according to thepresent invention comprises, a radio system providing data units(packets) of a particular MBMS service via a particularpoint-to-multipoint RB to the mobile terminal, the mobile terminalestablishes the point-to-multipoint RB and receives the data unitstherethrough, the mobile terminal triggers a timer when a data unit ofthe particular MBMS service is received, and the mobile terminalreleases the established point-to-multipoint RB if another data unit ofthe particular MBMS service is not received by the time the timer hasexpired.

Preferably, when another data unit is received before the timer hasexpired, the mobile terminal initializes and re-triggers the timer.

Preferably, a particular entity provided in the mobile terminal canoperate a timer for the data unit of a particular MBMS service. Thisentity can be located in the second layer (L2) of the radio protocol,and may be a MAC entity, a RLC entity, or a PDCP entity. If this entityin the mobile terminal operates a timer for a single data unit of thebroadcast or multicast service, and then does not receive another dataof the broadcast or multicast service before the timer expires, theentity in the mobile terminal reports the timer expiration to the RRC inthe mobile terminal. The RRC in the mobile terminal, upon receiving thetimer expiration report, performs the release of the point-to-multipointRB established for the broadcast or multicast service.

Also, a method for releasing the RB by a mobile terminal according tothe present invention comprises, a radio system providing data units(packet) of a MBMS service via a first point-to-multipoint RB andproviding status information of the MBMS service via a secondpoint-to-multipoint RB to the mobile terminal, the mobile terminalestablishes the first point-to-multipoint RB and receives a data unit ofthe MBMS service therethrough, and if the mobile terminal does notreceive another data unit of the MBMS service within a certain timeperiod, the mobile terminal receives the status information via thesecond point-to-multipoint RB and determines the release of the firstpoint-to-multipoint RB according to the status information.

Preferably, a particular entity provided in the mobile terminal candetect whether a data unit of the MBMS service is not received via afirst point-to-multipoint RB within a particular time period. Thisentity can be located in the second layer (L2) of the radio protocol,and may be a MAC entity, a RLC entity, or a PDCP entity. When theparticular entity detects that a data unit of the MBMS service is notreceived within the particular time period, this particular entityinforms the RRC in the mobile terminal of this detection.

Preferably, the RRC in the mobile terminal being informed of thedetection, receives the state information via a secondpoint-to-multipoint RB. If the state information indicates that asession of the MBMS service is not ongoing, indicates that the MBMSservice is not possible in the current situation, or indicates that theMBMS service is not provided via the first point-to-multipoint RB (i.e.,the MBMS service is provided via a point-to-point RB), the mobileterminal determines that the first point-to-multipoint RB should bereleased.

FIG. 4 depicts an exemplary method of how a terminal detects that a dataunit (packet) of a MBMS service is not received within a certain timeperiod. Preferably, an L2 entity (namely, a PDCP, RLC, or MAC entity)located in the second layer (L2) of the radio protocol in the mobileterminal is used to determine whether a data unit of the MBMS service isnot received during the certain time period while receiving the MBMSservice via a first point-to-multipoint RB.

In step 1 (S10), according to the RRC in the mobile terminal commands,the L2 entity in the mobile terminal establishes a firstpoint-to-multipoint RB. Also, the L2 entity in the mobile terminalreceives and stores a T_PTM value from the RRC in the mobile terminal.The RRC in the mobile terminal may receive the T_PTM value from a RRC inthe UTRAN.

In step 2 (S11), the L2 entity in the mobile terminal initializes thevalue of a timer T.

In step 3 (S12), the L2 entity in the mobile terminal operates the timerT for a data unit of the MBMS service.

In step 4 (S13), the L2 entity in the mobile terminal checks whetheranother data unit of the MBMS service has been received via the firstpoint-to-multipoint RB during a period based upon set units of time,such as a TTI (Transmission Time Interval). If the another data unit ofthe MBMS service is received within a single TTI, the terminal L2 entityperforms a subsequent step. If there is a data unit received within asingle TTI, the terminal L2 entity performs step 2.

In step 5 (S14), the L2 entity in the mobile terminal determines whetherthe timer T has expired. Namely, the current timer T value and thestored T_PTM value are compared to determine if the T value is greaterthan the T_PTM value, and if so, it is determined that the timer T hasexpired. If T is greater than T_PTM, the L2 entity in the mobileterminal performs the subsequent step. If T is not greater than T_PTM,the L2 entity in the mobile terminal performs step 4.

In step 6 (S15), the L2 entity in the mobile terminal reports to the RRCin the mobile terminal that the timer T has expired.

FIG. 5 depicts an exemplary method of releasing a point-to-multipoint RBused by a mobile terminal to receive data units (packets) of aparticular MBMS service according to the present invention.

In step 1 (S20), as explained with respect to FIG. 4, the L2 entity inthe mobile terminal establishes a first point-to-multipoint RB for aparticular MBMS service, and receives data units of the MBMS servicetherethrough.

In step 2 (S21), if a data unit of the MBMS service is not receivedwithin a certain period of time, namely, when the timer expires, the L2entity in the mobile terminal reports the timer expiration to the RRC inthe mobile terminal.

In step 3 (S22), upon receiving the report of timer expiration, theterminal RRC in the mobile terminal receives MBMS status (state)information from a RRC in the UTRAN to determine the state of theparticular MBMS service via a second point-to-multipoint RB. Preferably,MBMS status information comprises ID information of a MBMS service,whether a radio bearer has been established for the MBMS service,whether the established RB is a point-to-multipoint or a point-to-pointtype, whether a session of the MBMS service is currently ongoing or not,or whether the MBMS service may currently be provided or not. In moredetail, the MBMS status information is included in a control messagerelated to the MBMS, and transmitted to the mobile terminal via theMCCH. Preferably, the MBMS state information comprises a message thatinforms the MBMS service information or a message that informs thepoint-to-multipoint RB information.

In step 4 (S23), if in the above step, the received MBMS statusinformation indicates that an RB is currently not established, or if thecurrent RB type is point-to-point, or if a session of the MBMS is notongoing, or if the MBMS service cannot be currently provided, the RRC inthe mobile terminal instructs the L2 entity in the mobile terminal torelease the first established point-to-multipoint RB.

In step 5 (S25), the L2 entity in the mobile terminal releases the firstpoint-to-multipoint RB according to the instructions of the RRC in themobile terminal.

It should be noted that the present invention can perform thepoint-to-multipoint RB release method without step 3, namely, withoutreceiving MBMS status information. Here, the RRC in the mobile terminalreceiving a timer expiration report of the L2 entity in the mobileterminal performs steps 4 and 5, without step 3. In other words, the RRCin the mobile terminal receiving the timer expiration report of the L2entity in the mobile terminal immediately instructs the L2 entity in themobile terminal to release the first established point-to-multipoint RB.

As described above, the present invention relates to establishing apoint-to-multipoint (p-t-m) radio bearer (RB), receiving data of aparticular multicast or broadcast service, and if data of the particularmulticast or broadcast service is not received for a certain period oftime, determining to release the point-to-multipoint RB by checking thestatus (state) of the multicast or broadcast service. By using suchmethod, the terminal may effectively determine whether to maintainand/or release the point-to-multipoint radio bearer.

In other words, a terminal (e.g., mobile station, user equipment (UE),MBMS UE, etc.) according to the present invention can release apoint-to-multipoint radio bearer (e.g., a MBMS RB) in an explicit manneror an implicit manner. The explicit RB release mechanism allows thenetwork (e.g., UTRAN, etc.) to explicitly instruct the terminal torelease the point-to-multipoint radio bearer (RB). However, because suchexplicit instructions may not be properly received by the terminal incertain situations, the terminal also has an implicit RB releasemechanism that allows the terminal itself to release thepoint-to-multipoint radio bearer without receiving any explicitinstructions from the network. A more detailed example will now beconsidered hereafter.

In the explicit RB release mechanism, an MBMS UE releases an MBMS radiobearer in the UE side if receiving an explicit release message givenfrom UTRAN. This is a safe way because an MBMS UE releases an MBMS RBfollowing the explicit release message from UTRAN. UTRAN may need torepeat the release message to make sure that all relevant UEs completelyreceive it. A new signaling flow can be used for this purpose. However,an existing signaling flow, such as MBMS Service Information or MBMSRadio Bearer Information, can be also considered as an alternative. Acouple of possible ways of the Explicit MBMS RB Release mechanism aredescribed hereafter.

As a new signaling flow, the MBMS Radio Bearer Release signaling flowcan be considered to explicitly notify UEs of the MBMS RB Releasemessage. This signaling flow is applicable for handling MBMS to UEs inPMM IDLE and CONNECTED mode. The purpose of the signaling flow is forCRNC to trigger one or more UEs to release an MBMS radio bearer carryingan MTCH for an MBMS service. The MBMS RADIO BEARER RELEASE message isonly available for p-t-m transmission. The UTRAN may initiate thissignaling flow when a session is stopped for the MBMS service or whenthe MBMS radio bearer needs to be released for an RRM purpose. The MBMSRADIO BEARER RELEASE may be repeatedly transmitted after its firsttransmission. Upon receiving the first MBMS RADIO BEARER RELEASE, the UEshall release the radio bearer carrying an MTCH. The MBMS RADIO BEARERRELEASE message includes: a MBMS Service ID and a Cause (e.g. sessionstop). More information may be included in the MBMS RADIO BEARERRELEASE.

The MBMS RB Release Indication may be contained in the MBMS SERVICEINFORMATION message. If the MBMS RB Release Indication is included inthe received MBMS SERIVCE INFOMRATION message, a UE shall release anMBMS radio bearer indicated by the MBMS RB Release Indication.

The MBMS RB Release Indication may be contained in the MBMS RADIO BEARERINFORMATION message. If the MBMS RB Release Indication is included inthe received MBMS RADIO BEARER INFORMATION message, a UE shall releasean MBMS radio bearer indicated by the MBMS RB Release Indication.

The Implicit MBMS RB Release mechanism makes it possible for an MBMS UEto release an MBMS radio bearer in the UE side without receiving anexplicit release message or information given from UTRAN. This isnecessary owing to the fact that the Explicit MBMS RB Release mechanismis not sufficient at all times because some UEs may fail to correctlyreceive the MBMS RB Release message and encounter an abnormal situation.For instance, an MBMS UE may miss reception of the explicit releasemessage because of cell change, bad channel and so on. In those cases,the implicit mechanism may be necessary as a complementary solution,since it prevents the MBMS UE from unnecessarily keeping the MBMS RB. Acouple of possible ways of the Implicit MBMS RB Release mechanism aredescribed in the following sub-sections.

A UE uses a timer to implicitly release an MBMS RB by itself. During asession, the UE triggers a timer whenever a new MBMS packet is received.The timer will be re-triggered whenever another MBMS packet is receivedin the UE. In this case, the UE is simply able to decide to release theMBMS RB when the timer is expired. The timer value may be given fromUTRAN.

The MBMS Service Information signaling flow is used to inform UEs of allMBMS services in a cell. For this purpose, the MBMS SERVICE INFOMRAITONmessage includes MBMS Service Ids for MBMS services, which are beingserved or can be served in a cell. Thus, if the UE receiving an MBMS RBacquires the MBMS SERVICE IFNORMATION message, which does not containthe MBMS Service ID corresponding to the MBMS RB, then it is a right wayfor the UE to release the MBMS RB.

Accordingly, the present invention proposes the following MBMS UTRANarchitecture principles. For MBMS radio bearer release in the UE, the UEreleases the MBMS RB by using one of the following mechanisms: explicitMBMS RB release, and implicit MBMS RB release.

The explicit MBMS RB release mechanism allows the UTRAN to explicitlyindicate to the MBMS UE that an MBMS radio bearer should be released.The explicit MBMS RB release indication is included in a new MBMS radiobearer release message or in an existing MBMS service information orMBMS radio bearer information message. If the explicit MBMS RB releaseindication is received, the UE releases the MBMS RB.

The implicit MBMS RB release mechanism allows a UE to release the MBMSradio bearer without receiving the MBMS RB release message given fromthe UTRAN. Namely, a UE uses a timer to implicitly release an MBMS RB.During a session, the UE triggers a timer whenever a new MBMS packet isreceived. The timer will be re-triggered whenever another MBMS packet isreceived in the UE. When the timer expires, the UE implicitly releasesthe MBMS RB. Preferably, the timer value is given from the UTRAN. Then,the UE releases the MBMS RB if the MBMS service identification (ID)corresponding to the MBMS RB does not appear in the MBMS serviceinformation message.

The present invention can employ a variety of software, hardware, and/ora combination thereof to achieve the above-identified procedures andsteps for radio bearer (RB) release. For example, FIG. 6 depicts acommunication system comprising a terminal (UE 610) in radiocommunication with a network (UTRAN 620 and CN 630) according to anembodiment of the present invention. The network (UTRAN 620 and CN 630)may include various hardware and software components. For example, theUTRAN 620 comprises an RNC (626), being connected to a plurality of NodeBs (622), and having a processor (626-1) and a memory (626-2). An RNC(628), being connected to a plurality of Node Bs (624), may alsocomprise a processor (628-1) and a memory (628-2). The RNCs (626, 628)are connected with one another via an interface, and connected with theCN (630) via another interface. The network (UTRAN 620 and CN 630)handles the various processing procedures for communications with theterminal (UE 610) as described previously. Here, it should be noted thatvarious software codes and protocols that are required for achieving thepresent invention may be stored in one or more memory devices andexecuted by one or more processors located within the Node Bs (622,624), the RNCs (626, 628), and/or other network elements.

The present invention provides a method of controlling apoint-to-multipoint radio bearer used for a point-to-multipoint service,the method comprising: establishing a point-to-multipoint radio bearerfor receiving data packets therethrough; triggering a timer whenever adata packet is received via said radio bearer; maintaining said radiobearer if a subsequent data packet is received within timer expiration;and releasing said radio bearer if a subsequent data packet is notreceived within timer expiration.

Also, the present invention provides a method of releasing apoint-to-multipoint radio bearer used for a point-to-multipoint service,the method comprising: checking whether point-to-multipoint service datais received during a certain time period via a point-to-multipoint radiobearer; and if no point-to-multipoint service data is received duringsaid certain time period, releasing said point-to-multipoint radiobearer.

Additionally, the present invention provides a mobile terminal forreceiving a point-to-multipoint service, the terminal comprising: anantenna; a memory having software codes stored therein; and a processorconnected with the antenna and the memory, the processor executing thesoftware codes for, establishing a point-to-multipoint radio bearer forreceiving data packets therethrough; triggering a timer whenever a datapacket is received via said radio bearer; maintaining said radio bearerif a subsequent data packet is received within timer expiration; andreleasing said radio bearer if a subsequent data packet is not receivedwithin timer expiration.

Also, the present invention provides a mobile terminal for receiving apoint-to-multipoint service, the terminal comprising: an antenna; amemory having software codes stored therein; and a processor connectedwith the antenna and the memory, the processor executing the softwarecodes for, checking whether point-to-multipoint service data is receivedthrough the antenna during a certain time period via apoint-to-multipoint radio bearer; and if no point-to-multipoint servicedata is received during said certain time period, releasing saidpoint-to-multipoint radio bearer.

Furthermore, the present invention provides a communications network forproviding a point-to-multipoint service, the network comprising: amemory having software codes stored therein; and a processor connectedwith the memory, the processor executing the software codes for,transmitting point-to-multipoint service data to a mobile terminal thatchecks whether the point-to-multipoint service data is received during acertain time period via a point-to-multipoint radio bearer; andtransmitting point-to-multipoint service status information to themobile terminal if the mobile terminal determines that nopoint-to-multipoint service data is received during the certain timeperiod, allowing the mobile terminal to release the point-to-multipointradio bearer according to the point-to-multipoint service statusinformation.

Although various aspects, embodiments, and features of the presentinvention have been described for a UMTS communications scheme, many ofthese techniques can be advantageously applied for other communicationsmethods and systems.

The foregoing description of the preferred embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments. Thus, the present inventionis not intended to be limited to the embodiments shown herein but us tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. A method of releasing a multimedia broadcast/multicast service (MBMS)radio bearer (RB) used for a MBMS service, the method comprising:establishing the MBMS RB for receiving data packets of the MBMS serviceat user equipment (UE); receiving at the UE a MBMS service informationmessage; and releasing by the UE the MBMS RB if MBMS identificationcorresponding to the MBMS RB is not present in the received MBMS serviceinformation message, wherein the releasing of the MBMS RB by the UE isperformed without receiving at the UF a MBMS RB release indication froma network.
 2. The method according to claim 1, wherein the MBMS serviceinformation message is received from a radio network controller (RNC).3. The method according to claim 1, wherein the MBMS RB is apoint-to-multipoint RB.
 4. The method according to claim 1, wherein thereceiving of the MBMS service information message occurs via a MBMScontrol channel (MCCH).
 5. User equipment (UE) for receiving amultimedia broadcast/multicast service (MBMS), the UE comprising: amemory; a transceiver configured to receive a MBMS service informationmessage; and a processor configured to access instructions stored in thememory to: establish a MBMS radio bearer (RB) to permit the receiving ofdata packets of a MBMS service, and release the MBMS RB if MBMSidentification corresponding to the MBMS RB is not present in thereceived MBMS service information message, wherein the releasing of theMBMS RB is performed without receiving at the UE a MBMS RB releaseindication from a network.
 6. The UE according to claim 5, wherein theMBMS service information message is received from a radio networkcontroller (RNC).
 7. The UE according to claim 5, wherein the MBMS RB isa point-to-multipoint RB.
 8. The UE according to claim 5, wherein thetransceiver is further configured to receive the MBMS serviceinformation message via a MBMS control channel (MCCH).